This phase II trial is studying how well giving oxaliplatin together with topotecan works in treating patients with ovarian epithelial cancer, primary peritoneal cancer, or fallopian tube cancer. Drugs used in chemotherapy, such as oxaliplatin and topotecan, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving more than one drug (combination chemotherapy) may kill more tumor cells.